Calculation and analysis of long-term settlement of shield tunnel in weak stratum induced by train load

With the transformation of urban rail transit from construction period to operation-maintenance period in China, it is essential to study the causes of long-term settlement of shield tunnel in weak strata and its reinforcement measures. Based on the radial cement-soil pile reinforcement technology, Monismith's index model, layered summation method, composite foundation theory and other assumptions, a theoretical model is established to calculate the undrained plastic deformation of reinforced or unreinforced weak stratum under shield tunnel caused by long-term cyclic vibration train load. The applicability of the model is verified by monitoring data from practical engineering cases. Then, the influence of train load on the tunnel long-term settlement, the effect of stratum reinforcement under tunnel on the long-term settlement, and key points to design radial cement-soil pile are studied by parameters analysis. This paper may provide a new theoretical method for analyzing, predicting, and designing reinforcement schemes for mitigating long-term settlement of rail-transit shield tunnels in weak strata induced by train loads.